Most of today""s jet aircraft use bleed air extracted from a jet engine to prevent icing of the engine inlet (xe2x80x9canti-icexe2x80x9d) and as a source of air for aircraft compartments. For anti-ice, the bleed air is routed to the engine inlet area. For environment control, the bleed air is routed to an environment control system (ECS) which conditions the bleed air, generates low pressure cold air, and controls the cooling of avionics, heating, cooling and pressurization of the cockpit. Because the temperature and pressure of the bleed air as extracted from the jet engine is too high for the use directly by the ECS, the temperature and pressure of the bleed air are lowered before being supplied to the ECS.
The traditional method for supplying anti-ice and cooled bleed air to the ECS used by jet aircraft involves splitting the hot bleed air from the jet engine into two parts; the first part for anti-ice and the second part for the ECS. The first part is routed to inlet guide vanes of the jet engine through a pressure regulating/shutoff valve that is controlled by an ice detecting sensor located in the engine inlet. The bleed air passes through the inlet guide vanes, a nose cone, and spills out through a shroud of the nose cone and routed back to the engine inlet along the surface of the cone. The second part of the bleed air is routed to a heat exchanger that uses ambient or ram air as a heat sink. The heat exchanger cools the hot bleed air, and the cooled bleed air is supplied to the ECS.
To optimize aircraft performance, there is a constant demand for aircraft designers to improve on weight, volume, efficiency, cost, and certain tactical factors unique to military applications. However, the current method for anti-ice and supplying bleed air to the ECS comes at a substantial cost to flight performance. It requires a dedicated ram air circuit and a heat exchanger, two separate sets of ducts and valves, and an ice detecting sensor. These requirements increase cost, weight, volume, drag, and decrease reliability. Also, the front frame of the engine must be designed with heavier material in case of a valve failure, leading to an increase in cost and weight. Engine efficiency is reduced because there is a higher bleed air use during icing condition. Furthermore, the dedicated ECS ram air circuit for cooling the bleed air requires openings on the aircraft""s fuselage, increasing the aircraft""s radar signature. For the foregoing reasons, there is a need for a cooled bleed air supplying apparatus that is lighter, smaller, efficient, reliable, and allows for reduced radar signature.
The present invention comprises an improved apparatus for anti-ice and supplying cooled bleed air and a method for anti-ice and supplying cooled bleed air that substantially reduces disadvantages and problems associated with previous apparatus for anti-ice and supplying cooled bleed air.
According to one embodiment of the invention, an apparatus for anti-ice and supplying cooled bleed air to an ECS of a jet aircraft includes a modified front frame of a jet engine optimized for cooling bleed air with minimal pressure drop. A first duct routes hot bleed air from the jet engine to the front frame. The front frame utilizes the hot bleed air to prevent engine inlet icing and cools the bleed air. A second duct routes the cooled bleed air from the nose cone of the front frame to the ECS.
In a particular embodiment, the first duct routes the hot bleed air from at least one compressor stage of the jet engine to the inlet guide vanes of the front frame. The flow of the hot bleed air in the first duct is controlled by pressure regulating/shutoff valves. The second duct is positioned to route the cooled bleed air from the nose cone of the front frame to the ECS, supported by an aerodynamic vane.
The present invention comprises apparatus for anti-ice and supplying cooled bleed air and provides a number of important technical advantages over current apparatus for anti-ice and supplying bleed air. The apparatus of the present invention does not utilize a dedicated ram air circuit and a heat exchanger for cooling the bleed air. It also does not require an extra bleed air valve, a duct for the bleed air routed to the heat exchanger, an ice detector sensor and associated circuits, and the need for a heavier engine front frame in case of anti-ice valve failure. The simplification of the apparatus reduces cost, weight, volume, and increases reliability. Drag and radar signature is also reduced due to the elimination of the ram air circuit. Furthernore, the reduction in bleed air use in icing conditions increases the efficiency of the engine. Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.